Replaceable tong die inserts for pipe tongs

ABSTRACT

A gripping assembly for pipe tongs is provided to grip and rotate a pipe. The gripping assembly includes a pair of jaw assemblies that exert counteracting forces on the pipe. Each jaw assembly has a body with a cylindrical hollow defined in the body and having longitudinal slots formed in the body. The slots are separated from one another by longitudinal struts. In a cross section perpendicular to the longitudinal direction of the cylindrical hollow, flat faces of the slots form portions of a regular polygon. Each jaw assembly also has toothed tong die inserts that fit into the slots and provide for frictional engagement of the jaw assembly with the pipe. Each jaw assembly also has a first and a second end plate for retaining the tong dies in the slots with at least one of the end plates being removably attached to the body.

RELATED APPLICATIONS

[0001] The invention claims priority to U.S. Provisional Application No. 60/196,421, filed Apr. 12, 2000.

FIELD OF THE INVENTION

[0002] The invention relates generally to pipe tongs for gripping and rotating drilling pipe. More specifically, the invention relates to a gripping assembly of the pipe tongs having replaceable tong die inserts.

BACKGROUND

[0003] In handling a string of casing, drill pipe or tubing (referred to interchangeably as pipe), workers connect several segments of the pipe together. These segments of pipe commonly come in thirty-foot lengths. A typical way to assemble the pipe segments together is by a threaded pin and box connection. Several segments of pipe assembled together are often referred to as a drill string.

[0004] Workers use pipe tongs to thread or unthread pipe together to form or take apart a drill string. Typically, workers grip a first pipe segment while turning the second pipe segment with respect to the stationary first pipe segment. The pipe tongs perform two functions to assemble the pipe segments, namely gripping and rotating selected pipe segments. Ideally, the tong gripping mechanism, that often includes a tong die, slightly penetrates the surface of the pipe in order to maintain a positive grip on the pipe and to avoid crushing or permanently deforming the pipe.

[0005] Pipe tongs were originally powered by hand and to some degree still are. However, power tongs have replaced manual tongs in many applications. Power tongs are especially useful when a great deal of torque is needed to loosen a pipe connection.

[0006] Horizontal drilling, or directional drilling, is drilling in the earth at some angle to the vertical direction. Horizontal drilling is typically performed only when there is some obstacle to vertical drilling because horizontal drilling is much more expensive. With regard to pipe tongs, a worker performing horizontal drilling has to be capable of operating the pipe tongs at some angle to the vertical, sometimes at angles approaching ninety degrees.

[0007] There have been many patents directed to the construction and operation of pipe tongs and their components. For example, U.S. Pat. No. 6,079,509 issued to Bee et al (Bee '509) discloses a die set used in pipe tongs for gripping pipe while threadably coupling pipe joints. The die set taught by Bee '509 uses two semi-cylindrical pieces to grip a pipe. However, when a die set wears out, one must either discard the die set or carry out extensive machining to restore the gripping effectiveness of the die set.

[0008] U.S. Pat. No. 6,047,775 issued to Mock (Mock '775) teaches a pipe grip with two pairs of dies for loosening a drill pipe joint. A problem with the dies of Mock '775 is that the top surfaces of the dies are flat and therefore do not provide a precise, mating engagement of the dies with the pipe. This can lead to slippage between the pipe and the dies, which in turn can lead to mechanical failure of the pipe.

[0009] Thus, there is a continuing need for an improved jaw assembly for a gripping mechanism for pipe tongs that: (1) avoids the problem of slippage; (2) can be maintained easily in an unworn condition; (3) and is readily repairable when the gripping mechanism becomes worn.

SUMMARY

[0010] The present invention provides a gripping assembly for pipe tongs that grip and rotate a pipe. The pipe tongs are usable in horizontal drilling applications. The gripping assembly includes a pair of jaw assemblies that exert counteracting forces on the pipe. The counteracting forces are applied by rams which are typically hydraulically powered, but may also be electrically powered or powered by hand.

[0011] Each jaw assembly has a body with a cylindrical hollow and longitudinal slots separated by longitudinal struts. In a cross section perpendicular to the longitudinal direction of the cylindrical hollow, flat faces of the slots form portions of a regular polygon. Each jaw assembly has toothed die inserts that fit into the slots and provide for frictional engagement of the jaw assembly with the pipe. The jaw assembly also has a first and a second end plate for retaining the tong die inserts in the slots. At least one of the end plates is removably attached to the body so that the end plate may be removed, the tong die insert replaced, and the end plate re-attached to the body.

[0012] It is therefore a principal object of the invention to provide a gripping assembly for a pipe having replaceable tong die inserts.

[0013] Other objects, features and advantages which characterize the present invention will be apparent from the following detailed description and a review of the associated drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0014]FIG. 1 is a perspective view of a jaw assembly for pipe tongs of the existing art.

[0015]FIG. 2 is a front view of a gripping assembly of the present invention.

[0016]FIG. 3 is an isometric view of a jaw assembly for pipe tongs of the present invention.

[0017]FIG. 4 is a front view of a jaw assembly for pipe tongs of the present invention.

[0018]FIG. 5 is a side view of a jaw assembly for pipe tongs of the present invention.

[0019]FIG. 6 is a front view of a toothed insert that fits in a jaw assembly for pipe tongs of the present invention.

DESCRIPTION

[0020] Before discussing the present invention, it is useful to first consider a die of the existing art, as shown in FIG. 1. The die shown in FIG. 1 is part of a die set that grips a pipe in a tong assembly. However, it is easily seen that, if the die of FIG. 1 loses gripping effectiveness, it requires extensive machining to restore this gripping effectiveness. Furthermore, it is very expensive just to discard the entire die simply because the gripping surface of the die has worn. Thus, it is apparent that it would be much more cost-effective to have a replaceable gripping surface for the die.

[0021] Turning now to an embodiment of the present invention shown in FIG. 2, a gripping assembly 10 is positioned inside a housing (not shown) of either a rotation assembly or an assembly for holding a pipe 12 stationary. The gripping assembly 10 has two opposed jaw assemblies 14A and 14B. Each jaw assembly 14A (or 14B) has a base 16A (or 16B) connected to a ram 18A (or 18B) by placing a connecting pin 20A (or 20B) into connection hole 22A (or 22B) in the base 16A (or 16B). The ram 18A (or 18B) exerts an inward force on the jaw assemblies 14A (or 14B), which in turn exert opposed, gripping forces on the pipe 12. The ram 18A (or 18B) may be powered by a hydraulic system, by an electric motor system, by hand or any equivalent device.

[0022] In FIGS. 3-5, a single embodiment is shown of a jaw assembly 14 for a gripping assembly 10 of the present invention. In FIG. 3, the jaw assembly 14 has a body 24 with a cylindrical hollow 26 defined within the body 24. The cylindrical hollow 26 has the shape of a polyhedral cylinder, but will hereafter be referred to as simply cylindrical.

[0023] The body 24 also has longitudinal slots 28 formed within the body 24. Toothed tong die inserts 30 fit into the longitudinal slots 28. Teeth 32 of the tong die inserts 30 provide frictional resistance when a pipe is positioned between opposed jaw assemblies 14A and 14B, as shown in FIG. 2. This frictional resistance is critically important for the pipe tongs to grip the pipe 12 when assembling or taking apart a drill string.

[0024] A cross section of any one the slots 28 is generally trapezoidal or dove-tailed in shape, with a top boundary of each slot 28 being open. This cross-sectional shape for the slots 28 naturally retains the tong die insert 30 within the slot 28 in reaction to any force that would tend to dislodge the tong die insert 30 from the slot 28. Faces 34 of the slots 28 are flat and discontinuously form, in a cross section, an incomplete portion of a regular polygon.

[0025] It is important that the face 34 of the slot 28 is flat to permit easy sliding of the inserts 30 into the slots 28. This is particularly important for in-the-field replacement of the inserts 30 where the inserts 30 must be changed very quickly. The slots 28 are separated from one another by struts 36 that extend in the longitudinal direction of the cylindrical hollow 16.

[0026] A first end plate 38 and a second end plate 40 retain the inserts 30 in the slots 28. The first end plate 38 is removably attached to the body 24 with bolts 42. The bolts 42 screw into threaded bolt holes 44 in the body 24. The second end plate 40 is welded to the body 24. The end plates 38 and 40 are especially important for horizontal drilling. For vertical drilling, only a lower support end plate would be needed because gravity would keep the inserts from being dislodged from the upper end of the jaw assembly.

[0027] It is important that one of the first end plate 38 or the second end plate 40 be removably attached to the body 24. This permits one to temporarily remove the removable end plate, slide out an insert 30 after the teeth 32 have been worn down, put in a new insert 30, replace the end plate 38 or 40, and resume operation of the tongs. Connection hole 22 is formed in the base 16 for connecting the body 24 to a ram (shown in FIG. 2).

[0028] It should be noted that the end plates 38A and 38B shown in FIG. 2 has a slightly different geometry than the end plate 38 shown in FIG. 3. The end plates shown in FIG. 2 have a partial polygonal void defined in the plates 38A and 38B, while the end plate 38 shown in FIG. 3 has a partial circular void defined in the plate 38.

[0029] In FIG. 4, the jaw assembly 14 has a body 24 with a cylindrical hollow 26 defined within body. The body 24 also has longitudinal slots 28 formed within the body 24. Tong die inserts 30 (not shown in FIG. 4) fit into the longitudinal slots 28.

[0030] A cross section of any one the slots 28 is generally trapezoidal or dove-tailed in shape, with a top boundary of the slots 28 open. This cross-sectional shape for the slots 28 naturally retains the insert 30 within the slot 28 in reaction to any force that would tend to dislodge the tong die insert 30 from the slot 28. Faces 34 of the slots 28 are flat and discontinuously form an incomplete portion of a regular polygon.

[0031] It is important that the face 34 of the slot 28 is flat to permit easy sliding of the inserts 30 into the slots 28. This is particularly important for in-the-field replacement of the inserts 30 where the inserts 30 may need to be changed very quickly. The slots 28 are separated from one another by struts 36 that extend in the longitudinal direction of the cylindrical hollow 26.

[0032] A first end plate 38 and a second end plate 40 retain the inserts 30 in the slots 28. The first end plate 38 is not visible in the cross section shown in FIG. 4. The first end plate 38 is removably attached to the body 24 with bolts 42. The bolts are not visible in the cross section shown in FIG. 4. The bolts 42 screw into threaded bolt holes 44 in the body 24. Connection hole 22 is formed in the base 16 for connecting the body 24 to a ram 18(not shown).

[0033] In FIG. 5, the jaw assembly 14 has a body 24 with slots 28 (not visible) defined in the body 24. Tong die inserts 30 (not visible in FIG. 5) fit into the slots 28. A first end plate 38 and a second end plate 40 retain the inserts 30 in the slots 28. The first end plate 38 is removably attached to the body 24 with bolts 42. The bolts 42 screw into threaded bolt holes 44 in the body 24. The second end plate 40 is welded to the body 24. Connection hole 22 is formed in the base 16 for connecting the body 24 to a ram 18 (not shown).

[0034] In FIG. 6, an embodiment of a tong die insert 2304 is shown with a top face 46 that is arcuate. The top faces 46 of the inserts 30, when positioned in the slots 28, define an arc of a circle. The radius of the circle so defined substantially matches the radius of the pipe 12 being held in the jaw assembly 14. A bottom 48 of the tong die inserts 30 is flat to match the flat faces 34 of the slots 28.

[0035] For all embodiments of the present invention, it is also an important feature that at least three slots be formed in the body of the jaw assemblies. This permits the tong die inserts 30 to sufficiently encompass the circumference of the pipe 12 without having to use more than two jaw assemblies. Using more than two jaw assemblies greatly increases the cost of the gripping assembly. The combination of using (1) two jaw assemblies with (2) at least three slots 28 for each jaw assembly is a combination that provides an effective balance of gripping ability and cost effectiveness. For the particular embodiment shown in FIG. 2, the two jaw assemblies together encircle approximately two-thirds of the pipe.

[0036] In accordance with the foregoing description, a gripping assembly for pipe tongs is provided to grip and rotate a pipe. The gripping assembly includes a pair of jaw assemblies that exert counteracting forces on the pipe. The rams that are typically hydraulically powered. Each jaw assembly has a body with a cylindrical hollow defined in the body and having longitudinal slots formed in the body. The slots are separated from one another by longitudinal struts. In a cross section perpendicular to the longitudinal direction of the cylindrical hollow, the flat faces of the slots form portions of a regular polygon.

[0037] The jaw assembly also has toothed tong die inserts that fit into the slots and provide for frictional engagement of the jaw assembly with the pipe. Each of the slots has a trapezoidal shape that naturally retains the tong die insert in the slot in response to any force that would otherwise dislodge the tong die insert. The jaw assembly also has a first and a second end plate for retaining the tong dies in the slots. At least one of the end plates is removably attached to the body so the removable plate may be temporarily removed, the tong die insert replaced, and the removable end plate put back in place. Each of the tong die inserts has an arcuate top face and a flat bottom. When placed in the slots, the top faces of the inserts define a circle that has substantially the same radius as the radius of the pipe that is held between the jaw assemblies. A base of the jaw assembly connects the body of the jaw assembly with the ram.

[0038] Although the present invention has been described with respect to the embodiments shown in the drawings, those skilled in the art would appreciate that additions, deletions, modifications and substitutions may be made without departing from the spirit and scope of the invention as defined by the claims below. 

What is claimed is:
 1. A jaw assembly for pipe tongs with a rotation assembly housing, the pipe tongs being a device for rotating a pipe, comprising: (a) a body having a cylindrical hollow defined therein and having longitudinal slots formed therein; (b) tong die inserts fitting into the slots for providing frictional engagement of the jaw assembly with the pipe; (c) first and second end plates normal to the longitudinal direction to retain the tong dies inserts in the slots; and (d) a base attached to the body and to the housing.
 2. The jaw assembly of claim 1 wherein the slots are separated from one another by struts that extend in a longitudinal direction of the cylindrical hollow.
 3. The jaw assembly of claim 1 wherein, in a cross section normal to the longitudinal direction of the cylindrical hollow, flat faces of the slots form portions of a regular polygon.
 4. The jaw assembly of claim 1 wherein each of the slots have a partial trapezoidal shape in a cross section normal to the longitudinal direction of the cylindrical hollow.
 5. The jaw assembly of claim 1 wherein the first end plate is removably attached to the body.
 6. The jaw assembly of claim 1 wherein the second end plate is removably attached to the body.
 7. The jaw assembly of claim 1 wherein the second end plate is welded to the body.
 8. The jaw assembly of claim 1 wherein the second end plate is integrally formed with the body.
 9. The jaw assembly of claim 1 wherein the tong die inserts are substantially identical.
 10. The jaw assembly of claim 1 wherein top faces of each tong die insert are arcuate.
 11. The jaw assembly of claim 10 wherein, when the tong die inserts are positioned in the slots, the top faces of the tong die inserts substantially define an arc of a circle.
 12. The jaw assembly of claim 11 wherein a radius of the circle defined by the top faces of the tong die inserts is substantially the same as a radius of the pipe.
 13. The jaw assembly of claim 12 wherein a bottom of each tong die insert is flat.
 14. The jaw assembly of claim 1 wherein there are at least three slots.
 15. A gripping assembly for pipe tongs that grip and rotate a pipe, the gripping assembly comprising jaw assemblies for exerting counteracting forces on the pipe, wherein each jaw assembly comprises: (a) a body having a cylindrical hollow defined therein and having longitudinal slots formed therein; (b) tong die inserts fitting into the slots for providing frictional engagement of the jaw assembly with the pipe; (c) first and second end plates normal to the longitudinal direction to retain the tong die inserts in the slots; and (d) a base attached to the body and to the housing.
 16. The gripping assembly of claim 15 having two jaw assemblies that exert opposed, counteracting forces on the pipe.
 17. The gripping assembly of claim 16 further comprising a ram corresponding to each jaw assembly to apply an inward force to each corresponding jaw assembly.
 18. The gripping assembly of claim 15 wherein at least one of the first end plate and the second end plate of each jaw assembly is removably attached to the body.
 19. The gripping assembly of claim 15 wherein top faces of each tong die insert are arcuate.
 20. The gripping assembly of claim 19 wherein, when the tong die inserts are positioned in the slots, the top faces of the tong die inserts for each jaw assembly substantially define an arc of a circle.
 21. The gripping assembly of claim 20 wherein, for each jaw assembly, a radius of the circle defined by the top faces of the tong die inserts is substantially the same as a radius of the pipe.
 22. The gripping assembly of claim 21 wherein a bottom of each tong die insert is flat.
 23. The gripping assembly of claim 16 wherein the tong die inserts are in contact with two-thirds of a circumference of the pipe.
 24. A tong die insert for a gripping assembly for gripping a pipe, comprising: (a) a flat bottom surface; and (b) an arcuate top surface with a radius of curvature substantially equal to a radius of the pipe. 